The present invention relates to a plasma display panel and more particularly to a plasma display panel capable of improving the purity of a discharging gas by removing directly and effectively impurities within a discharging space.
As well known, a plasma display panel (referred to as PDP hereinafter), which displays a picture using a gas-discharge phenomenon, has been actively and increasingly researched and developed as a new generation display device such as a wall-hanging TV which can realize a large screen with its thin thickness.
FIG. 1 shows a structure of the most widely used AC PDP. As shown, electrodes E1 and E2 are on an upper substrate P1 and a lower substrate P2, respectively arranged so as to be orthogonal with each other and barrier ribs are formed to define discharging cells at the crossing portions of the electrodes E1 and E2. Formed on the space between the electrodes E1 and E2 is a discharging space into which a discharging gas is filled. A phosphor layer F is formed in the discharging cell so as to realize a predetermined brightness and contrast.
Meanwhile, a dielectric layer D is disposed on any one of the electrodes E1 and E2, for example, on the electrodes E2 when considering the PDP of a reflective type PDP in FIG. 1. When operating the AC PDP, wall charges are accumulated on the dielectric layer, triggering a discharging in the discharging cell, A protective layer may be formed, but not is represented in FIG. 1.
The upper electrodes E1 on the light transmission path are made of transparent electrodes, and in the case that there occurs a large voltage drop as in a large size display device, metal electrodes are additionally deposited thereon as bus electrodes. The lower electrodes E2 are commonly made of metal electrodes having a good conductivity.
However, such metal electrodes are composed of a metal material dispersed with a glass group ingredient, not a pure metal. Therefore, when sintering them or when operating the PDP, there may occur a problem that a metal ion emanating from the metal electrodes is diffused and migrated into adjacent functional layers.
To prevent it, a lower layer M is formed on the lower portion of the lower electrodes E2 in FIG. 1. Therefore, the migration phenomenon can be prevented and at the same time, a printing efficiency of functional layers such as electrodes can be improved.
However, in such a PDP structure, each of the functional layers E1, E2, B, D and the like is formed mainly by a printing method when manufacturing them; it is necessarily required to use a solvent in compounding a paste for a pattern printing. As the solvent, a volatile, organic solvent is mainly used in order to increase a drying speed.
The solvent is not completely exhausted in the course of drying and sintering the functional layers. As a result, the remaining solvent is slowly exhausted as an impurity only when operating the PDP, causing contamination of the discharging gas.
Accordingly, there is provided a getter for capturing the impurities and maintaining the purity of the discharging gas within the PDP.
FIG. 2 shows the conventional getter structures. As shown in the left lower portion of FIG. 2, an exhausting tube X is installed in the outside portion of the lower substrate P2, and a getter G is installed in the interior portion of a funnel formed by enlarging a connecting portion of the exhausting tube. In this construction, impurities within the discharging gas are captured through the discharging hole H.
However, since the discharging gas is isolated by the barrier rib, it is not easy to flow. Also, since the impurities are transmitted through only a small gap between the barrier ribs according to Dalton""s diffusion law, the getter installed into the exhausting tube of the outside of PDP does not have substantially any effects. That is, there exists a problem that the effect of the getter in capturing the impurities and maintaining the purity of the discharging gas becomes tiny.
In addition, there is another example of a conventional getter G. As shown in the right side of FIG. 2, a getter hole Hxe2x80x2 is formed at the portion opposite to a ventilation hole H, and a getter cup U having the getter G therein is formed tightly at an outer portion thereof.
In the above-described structure, in the case that a plurality of getters G are not installed, it is impossible to obtain the desired effect of the getter G. In order to install a plurality of getters G, a plurality of getter holes Hxe2x80x2 are required. As a result, the strength of the lower substrate P2 may be decreased, and the fabrication cost of the same may be increased.
In the other construction example of the conventional getter G, as shown near the center portion of FIG. 2, a groove C is formed at the lower substrate P2, and the getter G may be formed in the groove C by a printing method or a charging method. Therefore, in this case, since the getter G can be installed nearest the discharging space, it is possible to obtain a superior capturing effect, compared to the others. In the above-described structure, however, since the getter layer G is overlapped with a phosphor layer F as shown in FIG. 1, it is impossible to be effectively installed in the discharging space V on which the phosphor layer F is formed. Therefore, it is impossible to effectively remove impurities from the discharging space.
In addition, according to the U.S, Pat. Nos. 5,453,659 and 5,520,563 granted to Robert M. Wallace, et al. in the title of xe2x80x9cAnode plate for flat panel display having integrated getter and method of making a field emission device(FED) anode plate having an integrated getterxe2x80x9d, a plurality of electrically conductive regions are patterned on insulating layer. Conductive regions collectively comprise an anode electrode of a field emission flat panel display device. Luminescent material overlays conductors. An electrically insulating material is affixed to substrate in the spaces between conductors. By virtue of its electrical insulating quality, material serves to increase the electrical isolation of conductive regions from one another, thereby permitting the use of higher anode potentials without the risk of breakdown due to increased leakage current. A layer of a getter material overlays insulating material. A gap is left between the getter material and the luminescent material to maintain electrical isolation. However, differently from the FED, since wall charges are generated using a dielectric layer D and thus trigger a discharging in the PDP, it is impossible to additionally form such an insulation layer on the upper substrate P1 in the PDP.
Accordingly, it is an object of the present invention to provide a PDP capable of directly and effectively removing impurities from discharging spaces for thereby enhancing a purity of a discharging gas.
It is other object of the present invention to provide a PDP comprising a simple structure of getter layer, which can be manufactured at a low cost.
To achieve the above objects, in accordance with one embodiment of the present invention, in a PDP comprising an upper substrate and a lower substrate which are parallel to each other at a certain distance, a plurality of barrier ribs formed on the lower substrate for forming discharging spaces, address electrodes formed between each of the barrier ribs, a plurality of display electrodes formed on a surface of the upper substrate opposite to the lower substrate and crossing with the address electrodes, a plurality of discharging cells formed at cross portions between the address electrodes and the display electrodes, phosphor layers formed at portions between each of the barrier ribs, and a discharging gas tightly filled in the discharging spaces between the upper substrate and the lower substrate, a getter layer which is formed at a portion of each of the barrier ribs.
The getter layer can be prepared at portions of each of the barrier ribs with which the phosphor layer is not coated, by dispersing and forming getter material particles on an insulation material so as to have an electrical insulation characteristic.
Also, the getter layer may be independently formed at the upper portion of each barrier rib with respect to a discharging cell or may be formed to be crossed each other at every other cell with respect to a discharging cell formed in a direction that the barrier rib is extended. Even though the above structure may be formed by a sand blasting method, it can be formed easily and at a low cost by preparing a sheet which is consisted of powder layers bonded by a organic binder for forming the barrier rib and the getter layer, and by attaching the sheet to a given position of the discharging space and then sintering it.
The getter layer may be formed of a metallic compound which preferably has a black color. For example, the getter layer may be formed of element Zr, Ti, V, Al, Fe or the mixture of more than two elements among them.
As a result, the getter layer may be arranged in each discharging space, and it is possible to obtain an extended life span of the PDP by obtaining a certain purity of the discharging gas.
These and other advantages and features of the present invention will become more apparent from the description of the following preferred embodiment in reference to the accompanying drawings.